Dim txt1(textbox1.Text.Split(CType(" ", Char())).Length) As String
Dim txt2(textbox2.Text.Split(CType(" ", Char())).Length) As String
txt1 = textbox1.Text.Split(CType(" ", Char()))
txt2 = textbox2.Text.Split(CType(" ", Char()))

Dim diff1 As String = "" 'Differences between 1 and 2
Dim diff2 As String = "" 'Differences between 2 and 1

For Each diff As String In txt1
    If Array.IndexOf(txt2, diff.ToString) = -1 Then
        diff1 += diff.ToString & " - "
    End If
Next

For Each diff As String In txt2
    If Array.IndexOf(txt1, diff.ToString) = -1 Then
        diff2 += diff.ToString & " - "
    End If
Next
Response.Write("Difference in First To Second: " & diff1 & vbNewLine & "Difference in Second To First: " & diff2)